In heavy-duty levels it is important that the frame of the level maintains stability for accurate measurement readings. It is also important that levels, which are used in professional construction on types of jobs when a level may be dropped from a substantial height and be subjected to various stresses, sustain the impact with minimal or no damage.
Many box levels have a central vial positioned into a notch which is formed by removing a section of a top wall and adjacent portions of each side wall, as seen in FIG. 1.
Because material is removed from the center of the frame, a central frame section becomes the weakest portion of the extrusion. Tests have shown that in prior levels 10, the central region 11 of a frame 12 with the cut-out notch portion 20 for the central vial is substantially weak. FIG. 2 shows that in such prior levels 10 a bottom 21 of the notch 20 is the weakest region. Portions 22 of sidewalls 13 which surround the central-vial notch 20 are also substantially weak regions 22A which extend to weakened areas 22B.
It is further seen in FIG. 2 that there is also a substantial weakness in top-wall regions 23 adjacent to hand holes from which material is also removed from the level frame 12. There is a need for an improved level with a strong stable frame.
Levels include plural vials, almost always including a principal center vial which is parallel to a reference surface and used to indicate a horizontal orientation. Such horizontal vial is normally secured to the level frame in a position that permits viewing of the vial from both sides and also from above to ascertain the orientation of substantially horizontal surfaces. The most desirable positioning of such vial is within a topnotch in the body of a level which topnotch is defined by two sidewalls and the topwall of a hollow level body frame.
Most large levels also have end vials which include plumb and/or 45°-vials. Positioning of the vials presents a challenge for accurate securing of the vial to the frame. Such installation involves multiple steps, including calibration for accurate measurements. There is a need for an improved level which allows simple accurate mounting of the vial to the level body.